This invention relates to an electric water warming system capable of feeding hot water from a hot water storage tank and, more particularly, to an electric water warming system including a heating temperature controlling apparatus for the stored hot water.
An electric water warmer of this kind is utilized suitably for domestic use and operates such that water fed into a hot water storage tank of the water warmer is heated on, for example, a cheep late-night power to increase a temperature of a fed water and is stored in the storage tank as a hot water.
In a conventional art of this field, there is provided an electric water warming system of hot water storage type which comprises a hot water storage tank having generally a cylindrical shell provided with a bottom portion to which is connected a water feed pipe and an upper portion to which is connected a hot water flow-out pipe. A heating means such as a heater is mounted to an inside wall of the hot water storage tank so as to extend substantially horizontally and the heater is disposed at a portion near the bottom portion of the hot water storage tank so as to heat the water fed into the storage tank through the water feed pipe.
The water fed into the storage tank is heated by conducting electric current to the heater and the heated water gradually rises in the storage tank and stored therein from the upper portion thereof. Namely, the heated hot water is stored in the hot water storage tank with a temperature rising characteristic curve, substantially linear curve from the lower portion towards the upper portion of the stored water, so that the hot water temperature even at the lower portion is kept above a set temperature of a predetermined value.
However, since the temperature of the hot water in the entire hot water storage tank is regulated so as to be kept to the set value, when the hot water of high temperature in the upper portion of the storage tank is flown out rapidly in a short time outward through the flow-out pipe, the exhaustion of the hot water having a temperature above the predetermined value may be caused. In such case, it will become impossible to obtain a hot water of desired temperature required for a user for the reason that a lot of water fed through the water feed pipe cannot be rapidly heated to the set value entirely in the hot water storage tank even by the electric conduction to the heater, and accordingly, a hot water having a temperature below the set value will be temporarily stored. Therefore, there may be a case where hot water having a desired temperature cannot be utilized continuously, which results in defect in function of the hot water storage system of the type described.